Create a new project configuration so you could just pass the Configuration
property, i.e. ReleaseNewLib
:
<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'ReleaseNewLib|AnyCPU' ">
<DebugType>pdbonly</DebugType>
<Optimize>true</Optimize>
<OutputPath>bin\</OutputPath>
<DefineConstants>TRACE;NEW_LIBRARY</DefineConstants>
<ErrorReport>prompt</ErrorReport>
<WarningLevel>4</WarningLevel>
</PropertyGroup>
>